First things first, this is more complicated than it looks. It doesn't just rotate randomly. What it does is it takes 11 1-2 probability trials and multiplies them all together. Then it stores the result as a variable, points up, rotates (variable) degrees, and moves (variable) steps. And yes, it is random, but the pen sprite has a tendancy to stick to one side of the screen due to some outcomes being more likely than others.
I reccomend turbo mode.